1. Field of the Invention
The present invention relates to electronic paging systems, and in particular, to direct access electronic paging systems using digitally encoded radio frequency signals.
2. Description of the Related Art
Personal mobile pagers, or "beepers," have become increasingly common and more widely used. In particular, individuals whose occupations or personal circumstances require that they be accessible at all times, at least by telephone, find such pagers to be indispensable.
Typical electronic paging systems use radio frequency transmitters to access the individual mobile pagers associated with that particular system. A person wishing to page, or "beep," someone else's pager telephones the control center for the paging system. Either by conversing with an operator or entering information electronically over the telephone lines, e.g. via a Touch-Tone.RTM. key pad, the caller can specify which individual pager they wish to access. The appropriate access data is then transmitted over the radio frequency transmitter. The corresponding pager responds, e.g. by flashing a lamp, beeping or vibrating, thereby alerting its user that they are being summoned. More sophisticated pagers can also receive and display information informing its user as to the identity of the caller or the telephone number at which the caller wishes to be contacted.
Rising sophistication and falling costs of modern computer systems have allowed paging systems to become more sophisticated and less expensive to establish and operate. However, a major cost and obstacle to establishing and operating a paging system continues to be the radio frequency transmitter portion of the system. Dedicated radio frequency transmission systems can be and generally are quite expensive. Furthermore, obtaining a license and certification for the transmitter can be costly and very time consuming. With the advent and increasing use of such things as cellular telephones and other means of mobile communications, the radio frequency spectrum has become extremely crowded. Therefore, obtaining a frequency allocation and license for a new paging system is difficult, and in urban areas in particular, frequently impossible.
In rural areas this problem can be more acute. Aside from the expense and difficulty of establishing and licensing a paging system, profitability of operating the system may not be possible, depending upon the number of users or customers in the rural area. The area of coverage afforded by the transmitter may not include enough potential users to support the system.
Whether in urban or rural areas, these problems of cost, licensing and profitability of a paging system tend to reduce the number of systems competing in the marketplace. This lack of competition keeps user costs high and often tends to discourage any motivation among existing systems' operators to improve features or service.
One means by which a paging system can be simplified involves providing the capability for the users, e.g. customers, to initiate the paging signals themselves. For example, U.S. Pat. No. 3,818,145 to Hanway discloses a system in which the users, via individual telephones, can access the paging system to initiate their own paging signals. Thus, operation of the system from the perspective of the owner-operator can potentially be simplified. However, a dedicated radio signal transmission system is needed, which, as discussed above, is generally quite costly.
Another means by which a paging system can be simplified involves using already existing radio signal transmission equipment to provide the media through which the system's pagers can be accessed. For example, U.S. Pat. No. 4,908,828 to Tikalsky discloses a system in which a user, via a host interface, transmits paging signals over several FM radio stations which are tied together in a network. The paging signals are transmitted in the SCA ("subsidiary communication authorization") band, which is normally used to transmit background music, weather, time signals, educational information, etc. However, a network of several radio transmitters, accessed through a single host interface, are needed, thereby resulting in a high cost system, as discussed above. Furthermore, such a system interferes with normal usage of the SCA band.
Therefore, it would be desirable to have a simplified means by which establishing, licensing and profitably operating a paging system could be accomplished more quickly and economically.